Sen. Richard Shelby, R-Ala., speaks to Sinclair Broadcast Group about allegations of anti-Trump bias at the FBI on Jan. 24, 2018. (SBG)

WASHINGTON (Sinclair Broadcast Group) —

As some Republicans in Congress clamor for the release of a memo written by House Intelligence Committee staff under Chairman Devin Nunes, R-Calif., that reportedly alleges abuses of surveillance laws by FBI officials investigating President Donald Trump's campaign, Democrats are accusing Nunes of trying to discredit the bureau and special counsel Robert Mueller.

Sens. Richard Shelby, R-Ala., and Jim Risch, R-Idaho, acknowledged that FBI agents cannot be expected to be devoid of personal opinions, but they said there is some cause for concern that strong partisan views influenced the work of some officials probing Trump and Democratic nominee Hillary Clinton. On Wednesday, Shelby also expressed suspicion about a five-month gap in records of text messages between two agents who are under scrutiny, but the Department of Justice Inspector General's Office said Thursday it has begun recovering those messages.

Sen. Ron Wyden, D-Ore., defended Mueller's integrity and warned that efforts by allies of President Trump to undermine the FBI could provoke a constitutional crisis.